Array substrate is one of the main components of the Thin Film Transistor Liquid Crystal Display (TFT-LCD).
In the prior art, when a source, a drain and a gap therebetween are formed on an active layer through an etching process, in order to reduce the extent to which the active layer, as a whole, is affected by etching liquid or etching gas, the thickness of the active layer is generally manufactured thicker, for example, may reach 2000 Å to 3000 Å, thereby ensuring that even when the active layer is over-etched, the electrical performance thereof will not be greatly affected, and thus, the characteristics of the active layer and TFT switches are stabilized. However, the increasing of the thickness of the active layer will result in the increase in the off-state current of the TFT, which causes the problem that when the array substrate is used in a display device, because the off-state current of the TFT is large, the current used for displaying the previous frame of image remains at the time when the next frame of image should be displayed, so that the afterimage of the displayed image is relatively severe, thereby degrading the displaying quality. Meanwhile, when an active layer with a relatively large thickness is manufactured, the requirement for the manufacturing process thereof is more strict, and also more difficulty, which leads to a longer manufacturing cycle.
Accordingly, the TFT that is used commonly in the industrial field has a structure with an etching stop layer, that is, one silicon nitride (SiNx) or silicon dioxide (SiO2) film layer with dense structure and good insulation performance is provided at a place, on the active layer, corresponding to the gap between the source and the drain, thereby preventing the damage to the performance of the active layer at the time of forming the source, the drain and the gap therebetween. Meanwhile, due to the existence of the etching stop layer, it is not necessary to increase the thickness of the active layer additionally, the thickness of the active layer can be reduced to 300 to 1000 Å, and the thickness is greatly reduced compared with a case where there is no etching stop layer existing, thus, the off-state current of the TFT is relatively small, and the afterimage of the displayed image is slight when applying the TFT to a display device, so that good display quality of the display device is ensured.
However, since a process of forming an etching stop layer on the active layer is additionally added, at least five patterning processes are required to manufacture a bottom gate type array substrate with the etching stop layer, and specifically include: a process of forming a pattern including gates and gate lines, a process of forming a gate insulation layer, a process of forming an active layer, a process of forming an etching stop layer, a process of forming a pattern including sources, drains and data lines, and a process of forming pixel electrodes. Each of the patterning processes includes processes such as film forming, exposure, developing, etching and stripping. Obviously, the more the times of the patterning processes are, the higher the investment in the production facility is and the longer the manufacturing cycle is.
Therefore, how to reduce the times of the patterning processes when manufacturing an array substrate with an etching stop layer is an important technical issue that needs to be solved urgently in the related art.